1. Field of the Invention
The invention relates to a heat-resistant and fire-retardant coating composition which, upon application to a substrate and exposure to heat, decomposes and reacts to form a highly heat-resistant, thermal insulating and non-flammable barrier layer.
2. Description of the Prior Art
Intumescent, fire-retardant coating compositions containing carbonifics, film-forming binders and phosphorous materials are well known in the art. U.S. Pat. Nos. 3,562,197; 3,513,114; 4,009,137; 4,166,743 and 4,247,435 disclose such compositions containing ammonium polyphosphates as the phosphorous containing material. U.S. Pat. No. 3,969,291 describes the use of an amide polyphosphate condensate as a fire-retardant additive in an intumescent coating composition. U.S. Pat. No. 3,914,193 discloses the similar use of a crystalline form of melamine pyrophosphate.
U.S. Pat. No. 3,654,190 discloses an intumescent paint comprising a resinous binder, a blowing agent, a phosphorous containing material, a source of chlorine a solvent, an anti-settling agent, a pigment and a surfactant.
All of the prior art intumescent paint/coating compositions suffer from a variety of disadvantages. For example, the prior art compositions are relatively slow drying paints/coatings such that a relatively long drying period is required before any article onto which the paint/ coating was applied could be handled. These prior art paints/ coatings are also relatively soft and/or brittle and therefore prone to chip when subjected to rough handling. The prior paints/coatings are also water permeable and therefore prone to degrade when exposed to moist environments such as the sea. The prior art paints/coatings also suffer from the fact that it is difficult to form a strong adherent bond between the coatings and the substrate to which they are applied. Furthermore, the char formed by prior paints/ coatings were weak and were easily blown away if the fire had a velocity component, if there was a wind or by the velocity of the water from a fire hose.
Moreover, although prior art formulations provided a relatively high degree of fire- and flame-retardance to substrates to which they were applied, most intumescent fire protective paints/coatings did not weather well and have been relegated to mostly interior applications. These protective coatings/paints did not provide long duration protection against severe fires as high as 70,000 BTU/ft.sup.2 .multidot.hr. The paints/coatings did not perform in high velocity fires where the velocity of the burning combustion front was 59-73 ft/sec. The prior art paints/coatings were not required to provide long term protection against intense, high velocity fires. The prior art paints/coatings were also water permeable, suffered degradation when exposed to moist environments, and would not provide resistance to harsh operational conditions such as multiple impacts.
It is an object of the present invention to provide an intumescent coating composition which is not subject to the above-noted disadvantages.
It is a further object of the present invention to provide a substrate coated with an improved fire-retardant and heat-resistant coating.
It is a still further object of the invention to provide a method of coating a substrate with a composition which provides a high degree of flame-retardance and heat-resistance.